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Milwaukee now offers two different M12 3.0Ah battery packs – a compact battery, and an XC battery. What’s the difference?

Somebody asked this on the Garage Journal forum, and it’s a great question. The answer can be extended to questions about other battery platforms, but things can get messy since there are more variables changing. For instance, the new Dewalt 20V Max compact 3.0Ah battery pack has larger cells than the bigger high capacity 3.0Ah battery, and so things aren’t entirely relatable.

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The forum question asked about whether runtime is the same, with only the battery size changing.

While answering this requires making some assumptions in order to ignore several unknowns, hopefully my explanation makes sense. But also, please keep in mind that it’s been untested.

Light Usage

For light Milwaukee M12 tool usage, say driving small fasteners, powering an LED flashlight at low brightness, or powering a heated jacket at low heat, runtime should be similar.

For such uses, the compact battery pack has a small size and pricing advantage.

Heavy Duty Applications

This is where things change.

Given what I have seen in other examples, the Milwaukee M12 XC battery will have the advantage here.

Milwaukee’s XC batteries also given certain tools, mainly drills, a slight bump up in power. This has been true for M18 tools, but I don’t recall if I’ve heard of similar for M12 tools. Luckily, we know someone who recently tested things out – Doresoom Reviews.

It’s unclear as to which other tools XC batteries might provide a power or performance boost for, but there are other benefits as well.

Consider heavier duty work, where the power output of a battery pack increases. The compact battery pack might inch close to its output ceiling, and its internal temperature will increase, sometimes by quite a bit. A tool might then turn off, either due to over-current or over-temperature conditions.

Again, I’d like to remind you that this is all in theory.

The power output of an XC battery pack, will also increase in power output, but there’s greater overhead before it reaches on-paper limits. The battery pack’s operating temperature might still increase, but the XC pack should run cooler than a compact battery pack that’s being taxed under the same operating conditions.

Consider a situation where two barrels have to be filled with water. To fill the first barrel, one person is transferring water with a 3 gallon container. In the other boat, two people each have 1.5 gallon containers.

Let’s say the barrels are filled with 1 gallon per minute. The barrels will likely fill at the same rate. 2 gallons per minute? The person working alone might be filling their barrel a little slower. 3 gallons per minute? The team has more of an advantage.

If you’re saying “but 3 gallons of water doesn’t weigh all that much,” let’s say 3 gallons of cement. Or sand. Who will be faster or less fatigued, one person with a 3 gallon container, or two people with 1.5 gallon containers?

I’m not certain about 1.5Ah cells, but the last I checked, 2.0Ah and 3.0Ah cells had much higher maximum current discharge rates than 3.0Ah cells. This would make the 3.0Ah compact battery pack a little more prone to running hotter at high current operation.

This, in demanding applications, an XC battery pack should last longer, with less risk of over-current or overheating protections kicking in, at least compared to compact battery packs.

Size, Weight, and Ergonomic Differences

Compact batteries are smaller and lighter than XC batteries. This can be a convenience.

XC batteries have larger flat bottoms, allowing tools to stand up on a table, floor, or other stable horizontal surface. This makes it easier or at least quicker to set down and retrieve certain tools.

Pricing

The compact battery pack costs less than the XC battery, individually. Home Depot has a special on (2) packs of batteries, but the same is true for the XC battery.

If taking holiday season promo pricing into account, you can get (2) 3.0Ah XC batteries for less money than you can get (2) 3.0Ah compact batteries.

A 4.0Ah XC battery pack can be found for $69 at some retailers, $79 at others. If you’re just buying one battery, that gets you longer runtime than the 3.0Ah compact battery, for a proportionally less increase in cost.

Determining pricing advantages is tricky here. Things are somewhat close enough that pricing is probably the least important factor when comparing compact and XC batteries.

Summary

What it comes down to is what you plan to use the battery for. Will you be using it with a cordless saw? Heavy applications? Do you want to be able to set a tool down quickly, and have it at the ready for quick pickup? Or do you want your tool to be as small and light as possible?

If you want to guarantee maximum power potential, or the longest runtime in demanding use, the XC battery is likely the better bet. Stepping up to the 4.0Ah XC battery provides added advantage.

If you want to be able to set a tool down with greater stability, the XC is the better choice.

If you want a smaller and lighter tool, the compact should serve you well.

If you want the most bang for the buck, make a table and determine which battery will give you the most amp-hours of charge capacity per dollar.

The XC 6.0 is available from Home Depot it anywhere else that sells Milwaukee. I’m using all 3.0 compact packs and 6.0 XC packs nowadays. They are great. There is zero reason for anyone to get that 3.0 XC pack described in the article nowadays. It is far outdated. If shopping for an XC pack, at least get a 4.0, if not the 6.0.

I only have a 3.0 XC pack because it was included as a freebie with the spot light. Otherwise I completely agree, there’s almost no reason to get a 3.0XC anymore. The 4Ah seems to have better than a 25% runtime increase, and is just as cheap anymore, plus easy to get for free with a deal if you wait a bit.

On the M12 circular, the 3.0 XC definitely gives a slight bump in power over the compact, it binds up less. The 6.0XC also seems to give another slight bump over the 3.0XC. My guess would be the newer batteries used in the 3 CT and the 6 XC have slightly higher current delivery ratings than the previous batteries, but probably not 2x higher, which is why the 3.0XC still gives a performance bump.

I mostly use the 2Ah and 3Ah compacts in everything except the SDS, Vacuum, and circular saw. Unless I really need the runtime (like in a light that I’m not holding), the compact batteries are less weight and size, and IMO that makes them hugely more convenient.

Yeah. I’m sure the 3.0 compact and the 6.0xc probably use the 3.0ah LG HG2 18650 cell. I did some testing with these m12 battery packs and they did not quite double the older 1.5ah cell packs or have 50% more than 2.0ah cell packs, but it was pretty close to that however. The consensus on the Internet has always been that the HG2 is slightly over rated and is really about 2900mah. It’s still a darn good cell though, I wish it got used more. I don’t like these monster truck battery packs using 3.0ah 20700 and 21700 cells nowadays.

As Jalopy J says …we use only compact 3 or the big 6…why would anyone waste money on a big 4 or 3 or compact 1.5 or 2…? To save $10 or $20 that’s insane….
There is a big difference between the XC 3 and XC6 ……there is almost no noticable difference between the compact 3 and the XC3……zip!
I do love theory’s and YT guys that make videos ,but don’t use the tools everyday…one test in your garage is not a test for anything, but it is comical.
Go get the compact 3 and big ol 6 and use the M12 tools as they should be used.👍

I have noticed that the XC battery that i have does have more juice. But i believe it is a 2.0 and 4.0 for the comparison… I think just about all of my 2.0 m12 batteries are just about trash. They’ve lived in my truck tool box for a couple years- maybe 4?

I was looking at some off brand m12 batteries on amazon. does anyone have any GOOD experiences with some of those m12 batteries?

Batteries are one of those things you need to treat as an expense item. They are not quite consumables (like sanding sheets) – but do have a finite life. If they are part of your business – hopefully you generate an adequate income stream that needed replacements don’t adversely impact your cash flow. If you use them as part of a hobby – then you need to fit them into your cost-benefit (enjoyment from the hobby) tradeoffs. For the manufacturers, I suspect sales of batteries are a high-profit part of their business. When the M12 line was just starting off – we tried several tools out for our plumbing and installation businesses. They came with 48-11-2401 – 1.5Ah batteries. Our experience with NiCad and NiMH battery powered tools – suggested that we be cautious and not overstock the original batteries. That proved useful – because as the M12 tool line took off – so did the introduction of more capable batteries – starting with 2.0Ah and 3.0Ah XC batteries. Like others have said – buying today I see no compelling reason to buy the lower Ah batteries for the M12 line as they don’t seem to offer great cost and size advantages.
In another business – we were using Makita 18V tools – and some of our early BL1830 batteries had charging issues – perhaps a reason to spread your battery purchases out to avoid the potential of getting a defective batch. Not that Makita and/or our supplier did not make good on the defective batteries – but its not very productive to buy and have to return stuff when you need it to get your work done.
I feel the same way about tool warranties. All things being equal – I’d prefer to have a tool that works well for its intended purpose – and lasts – rather than having one that has to be repaired or exchanged under warranty. When a tool is out of service – it is not making money for you – and in fact you need to devote wasted time to have it serviced or replaced. There is also a cost of keeping spares or running around to buy replacements associated with unreliable tools.

Just buy the real ones on ebay. You can get 2.0’s for about $25, 4.0’s for a little under $40. And 6.0’s for a little under $50. Just make sure your paying attention and get actual Milwaukee batteries instead of the ones that say “for Milwaukee.”

As an Aussie looking in on the American market, it seems to me that there is a lack of high capacity battery uptake over in the USA. Over here every one want the biggest baddest packs you can get, yet Milwaukee America seems happy to sell kits with 2-0 or 4-0 packs…?

To be fair, we don’t get any M12 kits with 6.0ah batteries in Australia either.

But I do get your point, although there are cases where you would and do choose a smaller battery, why settle for a lesser battery when they weigh the same and are the same size.

I have bought 2 x 6.0’s on top of the existing 3.0’s and 1.5’s I still have, but nearly always grab the 6.0’s first though. Especially for the M12 circular saw. 1.5’s only get used in the heated hoodie.

I don’t have any of the 3.0 compact packs but I do have 2 1.5’s, 2 4.0 XC and 1 2.0. Recently I was using the 2.0 to drill some pretty heavy duty holes with my M12 gen1 drill and I started having strange problems with it cutting out. I thought there was something wrong with the drill at first but then I realized it might be the smaller battery. I popped in a 4.0 XC battery and I had no more issues. Since that time I pretty much use the 4.0 XC batteries in my drills and impacts. Longer run time, more power, and a larger surface to stand the tool up!

I have all of these. I inadvertently bought a couple of XC 3.0 batteries thinking they were 4.0. I have both of the compact. I also have a 6.0. that came as freebie. They all work just fine. There does seem to be more power with the large 4.0 and 6.0 batteries, and of course more run time.

It’s pretty simple: for small jobs when I want a lighter tool, I use the compact batteries. For drills in particular they are a joy to use. When I’m driving deck screws for hours I use the larger batteries.

I didn’t see this mentioned yet, but real quick note. (after typing this, I realized this is not quick and contains math. My bad). Lithium ion batteries are rated at something called ‘C’ (stands for coulomb). 1C means the battery will go from full charge to empty in 1 hour. a 3AH battery can provide 3 amps for 1 hour. A 2AH battery can provide 2 amps for 1 hour. In both cases, the 1 hours means 1C.

These 2 battery packs get to the 3AH rating differently. A 3AH lithium ion battery at 12v can be 3 batteries in series where each battery should be rated for 3AH at 1C. The bigger battery pack is 6 batteries, 2 sets of 3 batteries in parallel where each individual battery is rated for 1.5AH.

In a perfect world, the batteries are identical and division can be used to get runtimes. For either battery, you should get 3 amps for 1 hour at 12v from a 3AH battery. That implies you should be able to get 1.5 amps for 2 hours (one half C), or 6 amps for 30 minutes (2C). Unfortunately, that is not the case. Physics is a cruel mistress.

The faster a battery is drawn down (higher C rates), the less power can be served by the battery. Conversely, drawing at lower power (lower C rates) the more power is available. In addition to the AH/C rating, lithium batteries are rated in terms of maximum amperage. For lithium ion, often this is over 15 amps, but can be way higher than you expect. For example, The lithium ion batteries I made by 52v bike battery pack out of (Samsung INR18650-25 cells, about $8 each) are rated at a continuous 20 amps each, but can burst to 100 amps for a few seconds. That pack is made of 14S4P (14 in series, 4 in parallel for a total of 56 batteries) and can sustain 80 amps at 52 volts from full to empty while It can spike to 400 amps for startup/acceleration. Those batteries are rated at 2500mah, or 2.5AH at 1C. So if I tossed those batteries into the Milwaukee plastic case, I would have a 2.5AH battery that could burst to 100 amps at 12v. That equals 1200 watts, but it could only be sustained for perhaps 10 seconds.

What that means for tools, and specifically for these 2 packs is that all things being equal, the 3AH pack with 6 batteries will have more usable power in nearly every use case. The amount of additional power available depends on the specific amp draw, power profile and the cells that the pack is made from. I can’t find anything online about the cells in the 2 packs, and I don’t have either of the packs to tear down.

The easiest way to measure for low amp draw tools (like a flashlight) is often by watt-hours. This rating is almost always calculated at 0.2c (a 5 hour discharge from full) for lithium ion batteries, or an abysmal 0.05c (20 hour discharge) for lead-acid and alkaline. Watt-hours measured at 0.2c is a very common metric that is often stuck on a battery somewhere or in a manual. Sadly, it is not a universal metric. The only fool-proof way to tell true capacity and runtimes are to tear apart the packs, check the cells, and look up their true capacity curves from the battery manufacturer. So many pack manufacturer over-rate batteries, but Samsung and LG (makers of the cells themselves) do not. This is why you can go on fleabay and find 10000 mah (10AH) batteries when in reality they are probably under 1.5AH. As far as I know, no manufacturer makes a 18650 battery cell over 3.5AH at 1C and even 3000 mah (3AH) cells are difficult to find (LG makes one, which are probably the ones in the 3AH pack)

As a further note, the reason the 6 cell battery may give a tool more ‘pep’ is due to voltage sag. The higher the C draw, the more voltage sag there will be; all things being equal. If the 3 cell battery drops to 10v under load while the 6 cell drops to only 10.5, the 6 cell will feel more powerful because it truly is more powerful. That half volt can be 25 watts of power extra that a motor will use at the same amperage. Motor controllers are generally amperage controllers since amperage has a direct correlation to the heat the motor will generate and thus need to dissipate.

This is something that can be tested, but you need to generally drill holes in the tool or battery to attach voltage sense wires if you can’t find the spec sheet. We can make up an example though, using the same ratios as the INR18650-25 battery that I have the spec sheet for.

Let’s say the brushed 12v Milwalkee will kill a 3 cell 3AH battery in 15 minutes of 100% load run time. That means the drill is pulling 12 amps for 15 minutes. The voltage drop on the INR18650-25 at that profile would be from a nominal 3.6v to a loaded 3.2v. that means the motor would be seeing 9.6v (3.2v times the 3 cells) at 12 amps, which is 115 watts. If we went to a pack of 6 of the same INR18650-25 batteries, we would see a few things. First, the rating of the pack would go from 2.5AH to 5AH. That means if all things were equal, we would get 30 minutes of run time instead of 15. For purposes of this, we don’t care about the runtime; we care about WHY the runtime doubled. This is because the amperage draw from each battery is now half of the 3 cell version. The draw is now 2C with 6 cells instead of 4C with 3 cells. At 2C, the voltage drop for the INR18650-25 is from a nominal 3.6v to a loaded 3.51v. The motor controller is still pulling the same 12 amps, but the motor is now seeing 10.5 volts, which is 126 watts.

Doubling the count of identical cells from 3 to 6 didn’t just double the runtime, it also increased the motor power from 115 watts to 126 watts because of the lower voltage drop. The motor now has almost 10% more pep for an identical amp draw.

You cannot go by on-paper specs. For instance, Milwaukee says that you cannot go by the spec sheets for the 3.0Ah cells they use in certain packs, because the cooling from their pack designs allows them to push past paper specs.

For instance, 2.0Ah cells are rated on paper to around 1.2C. 2.5Ah cells to maybe 0.9C. And 3.0Ah cells to maybe 0.5C.

A 9Ah pack with 15 cells should be rated to 45A max current on paper, while 10 cell 4.0Ah and 5.0Ah packs should be rated to maybe ~50A and ~44A respectively, going by the last ratings I saw. But in application testing, the 9Ah pack runs cooler and longer.

Milwaukee is the company providing the warranty on the battery, not the cell manufacturer and most lithium ion batteries are rated for between 400 and 600 full charge cycles to 4.2v per cell. Milwaukee is taking on the fiscal risk of battery pack death by drawing more amperage, not the cell manufacturer. According to Milwaukee’s warranty page here: https://www.milwaukeetool.com/Support/Warranty the batteries are warrantied for between 1 and 3 years.

In any case, for all but the hardest users, 600 charges is more than the expected lifetime of a lithium ion battery. The INR18650-25 that I was talking about earlier has a stated capacity of 2500mah (2.5AH), but on the 220th charge cycle its capacity is 2000mah (2.0 AH) at a 2C rate. At a discharge rate of 80 amps/32c, it takes 100 cycles to drop the capacity to 2AH. Lithium ion batteries have a finite lifetime that varies slightly by chemistry; generally accepted in the industry to be about 3 years for a 18650 battery (most of the batteries in power tools are 18650). Capacity drops off starting immediately, even if never used and left at their nominal long-term storage charge state of about half charge. The INR18650-25 that I mentioned loses 3% capacity (2500mah to 2425mah) with zero use at the 50 day point after manufacture. That’s just a thing with lithium ion chemistry. For most users, they will die by the calendar, not by over-use.

Dewalt charges their batteries to about 4.1v per cell (in their 20v max tools anyway, I tested with my multi-meter) instead of the more standard 4.2, and that tends to nearly double the life of the cell for charge cycle life expectancy. I don’t know if Milwalkee does something similar, but they may. The 0.1v reduces capacity minimally but I assume has a large impact on warranty costs for the company.

The chemistry of a cell dictates when it needs to stop being discharged, and that trigger is internal temperature. At about 350 degrees, a lithium battery will auto-ignite, and the fire is self-sustaining. If a cell is discharged fast enough though a fault, the internal heat will rise faster than it can be transferred to the case of the battery and thus to the thermocouple that would shut off the battery or tool. Anything over about 200 degrees starts drastically effecting lifecycle too, so most thermal cutoffs are well under that. lithium ion cells are currently tested as a nearly short circuit (I believe 20 miliohm) which is about 200 amps at a full charge voltage. They are not allowed to overheat/ignite from a full charge to whenever they are dead with that short circuit. I believe they are allowed to smoke/outgas in the ISO test but I don’t have the failure modes handy; I believe there are 5 states if I remember correctly, and a fire or explosion are the 2 that cause a test failure.

A heatsink, forced air, or similar cooling will keep the battery in the safer range while amperage draw (or charge rate) is over the normally rated amount. What that means is that the long term capacity of the battery will not be affected as much because the battery will not get as hot as it does in the normal testing. Time and heat (and charging while cold) are killers of lithium ion. The molecules that hold the electrons change shape with each charge/discharge, over time they get less elastic, and heat makes it worse.

Milwaukee may say that their batteries perform better than what the manufacturer of the cells state, but they (or any battery pack manufacturer) can’t change the basic chemistry or physics involved. They can certainly improve the number of charge/discharge cycles with cooling or make up for drawing more than rated amperage from a cell with less capacity loss over time. However, Milwaukee (or any manufacturer) can’t realistically get more amperage, voltage, or wattage from a cell then the manufacturer can.

If Milwaukee says we can’t go by paper specs, which specs are they referring to? Some are impossible to change. Electrons can’t be created, the lattice of the lithium ion anode and cathode can’t be externally modified, the same destructive heat is generated for each electron that is withdrawn. However, Milwaukee can change how much that heat lingers in the cell and thus effect cell charge/discharge cycle counts and capacity loss caused by that heat.

As a note, your example of the 4, 5 and 9AH battery packs call out max amperage. Max amperage doesn’t matter all that much since a tool is not going to draw max amperage for long. A battery can also put out more than it is rated for, but it will shorten lifespan. The voltage sag at whatever amperage the tool is pulling will determine the wattage available to the tool.

Look at it this way: The 4AH and 5AH packs you mention sound like ~18v nominal (20v marketing) 10 cell packs of 2.0 and 2.5AH cells (in 5S2P orientation) respectively while the 9AH would be a 15 cell pack (in 5S3P) of 3AH cells.

Let’s say those are all being used in the Milwaukee 2736-20 table saw. That saw supposedly performs like a corded 120v version. The maximum amount of wattage that is allowed per electrical code in the US to be pulled from a 15 amp 120v outlet is 1800 watts, so let’s say the saw has a 1800 watt motor. To get to 1800 watts, the battery, whatever it is (as long as it is 18v nominal), needs to put out 1800/18=100 amps. Therefore, the saw (wiring, motor, etc) should be built to handle 100 amp draw. The controller is very likely set to draw 100 amps max (again, assuming the marketing)

The 4 and 5AH battery packs are both made of 5 cells in series (3.7v times 5 = 18.5v but I will use 18v because it makes the math pretty) and then 2 of those strings in parallel. That means each set of parallel cells in those packs is serving 50 amps since there are 2 parallel sets in the pack. This is over the rating you mentioned of ~44A for one of the packs, but the pack is not always serving the full 1800 watts and 100 amps; it would only be when under heavy load. I would expect the voltage of the 44A rating to sag more than the others, and thus be unable to provide the full 1800 watts asked for by the controller (voltage probably drops to 16 or17v instead of 18). I would thus expect the saw to perform sub-optimally with that specific pack, but the saw would still work as long as the cell voltage stays above about 3v (15v for 5 cells in series)

The 9AH pack has one more parallel battery string of 5 cells, so each cell only needs to provide 33.3 amps to get to the same 100 amp output. In addition, since we are not pulling as much amperage, there should not be as much voltage sag, so the voltage (and thus wattage) would be slightly higher than 1800 watts expected. That would be why the performance is better using that pack. The 9AH pack would also run the saw longer because each string is only providing 33 amps instead of 50. That gives the 9AH pack a lot more thermal headroom. In addition, the 15 cell pack has more mass, so it takes longer to heat up. The pack is also psychically larger, so it can radiate more heat into the enviroment. All 3 of those (less amps per cell, more mass, more surface) add up to make the 15 cell pack run cooler than the 4AH or 5AH packs. The lower amp draw per cell gives the 9AH pack more performance due to less voltage sag.

SO…in lehman’s terms( regular consumers)….the bigger the amp hour number the more work can be done in the same amount of run time….example…if a 1.5 ah m12 compact battery will drive 150 screws before it drops off,..then a 3.0 compact battery will drive maybe 300 in the same amount of time…,roughly….??..anyway i dont want 1.5 or 2.0 compacts…i want 3.0 compacts…if you want to step up power a bit more, then the 6.0 bigger battery can do that….any other batteries do less work for their size…so a 3.0 compact will do the most work for its size and 6.0 for its size…the annoying thing is that milwaukee doesn’t sell tools WITH EITHER!!!!…they are forcing you to buy the aged and outdated lesser batteries, as you have to buy these better batteries as an accessory…so when it feels like you are getting a great deal by buying combos, keep in mind you are not buying them with the latest and greatest batteries even though the tool, (like the new stubby impact,or latest12v hammer drill and impact combo)..that just hit the market is the latest and greatest….tells me that the must be overstocked or to invested in, alot of the lesser batteries…..its keeping me on the fence….!!…scratchin my head…

Higher capacity batteries, which have 10 cells (or even 15), compared to 5 cells for compact battery packs, can be considered as being larger gas tanks and with a second fuel pump.

Most people shop by price. Let’s say there were two versions of a kit. $199 with 4.0Ah batteries, or $249 with 6.0Ah batteries. Which do you think more people will buy? Or let’s say a Fuel kit with 5.0Ah batteries for $299, or 6.0Ah batteries for $329. Which will more people buy.

Most if not all brands do this – they bundle their kits with now-midsized battery packs, rather than the latest and highest capacity ones. Milwaukee sometimes does bump up what is bundled in new kits, but they don’t (often?) update older kits to include new battery packs. Why should they? Doing so would likely require a bump-up in price, and that’s not a good idea.

A lot of the time, the mid-sized battery packs offer better price-per-amp-hour cost breakdowns. I wouldn’t call them “aged, outdated, and lesser.”